This invention generally relates to a tracking system which is employed in a video tape recorder/reproducer, and more particularly to a system for generating a displacing pattern signal applied to a positionable element on which a video head is mounted so as to maintain the video head in substantially undeviating configuration with respect to a recorded video track.
Recently, an automatic tracking system has been introduced for a video tape recorder/reproducer. Such a system makes possible the proper tracking of the video track recorded on a video tape, reproducing no noise band pictures regardless of the tape speed mode, (for example, normal speed mode, slow motion mode, still motion mode, quick motion mode, reverse motion mode, etc.).
In the conventional automatic tracking system, video heads are mounted on respective positionable elements such as piezoelectric elements. Each positionable element is dithered by a signal from an oscillator. The tracking error signals are detected from the envelope of reproduced signals. According to the resultant tracking error signal, a negative feedback (NFB) loop controls the positionable element so that the video head properly follows the recorded track.
In the case of the automatic tracking system described above being applied to a video recorder/reproducer employing a narrow video track width, (for example, a 20 micrometer track width), the displacing amplitude of the video head due to the dither signal is restricted to a range of a few micrometers.
Accordingly, the tracking error signal obtained from the envelope signal is a signal having a very low SN ratio. To improve the low SN ratio of the tracking error signal, it is necessary to use a L.P.F. having a very low cutoff frequency in the NFB loop. Since the transient response of the NFB loop is limited by the L.P.F., some noise bars appear on the reproduced pictures during a reproduction mode change.